Hermetically sealed housings are used to protect the parts located therein from undesired external influences. Hermetic housings are likewise used for the protection of high-quality and sensitive microelectronics. These housings establish the connection of internal components to the outside environment by, for example, glazed vias. The components in this respect are securely protected against any type of external influences such as radiation, sparks, gas and air as well as liquid media.
Hermetically and electromagnetically sealed housings for the protection of sensitive electronics are above all used in aerospace electronics as well as in defense technology. It is known to accommodate hybrid circuits of passive and active electronic components in a metallic housing and to close it in a sealed manner while filling with inert gas.
Different sealing concepts are known such as the water-resistant housing structure disclosed in the publication DE 10 2005 040 844 A1. This housing structure is admittedly only sealed against fluids, but not against gases, which is in particular of special importance in aerospace applications due to the extreme environmental influences.
An electronic box of an aircraft can have a very large capacity. A large sealing surface thus results due to the plurality of plugs and covers. The sealing concept must satisfy very high and atypical demands due to the pressure differences between the internal pressure and the external pressure of several bars which arise in the air.
In the previously known hermetic housing arrangements which were in particular used in aerospace technology, there were continually problems in the past not only with respect to bonding and leak-tightness, but also problems with respect to corrosion. Previously, elastically deformable plastics such as fluorosilicone rubber (FVMQ) were used as sealing material for these known housing structures. As is known, fluorosilicone combines the good high-temperature properties and low-temperature properties of silicone with good fuel resistance and oil resistance. Fluorosilicone O rings as seals are, however, above all used in fuel systems at temperatures up to 177° C. as well as in applications in which the resistance of silicone to dry heat is demanded. Fluorosilicone is as a rule only recommended for static applications due to the relatively low tear strength, the high friction and the insufficient wear properties of this material.
U.S. Pat. No. 4,960,391 describes a classical sealing solution of hermetic plug connectors in which an O ring seal, which is produced from elastomer as a rule, has to be let into a groove. It is of disadvantage in this solution that crevice corrosion and contact corrosion forms at the plugs and at the housing. The risk of crevice corrosion is present at the housing cover. It was proposed in this document to use a paste which is intended to serve as corrosion protection, but does not ensure any complete protection. A further disadvantage of such solutions is that the O ring is very sensitive due to the pressing. Too high a pressing of the O ring seal results in damage and thereby to the failure of the seal. Too low a pressing, in contrast, has the consequence that the desired leak-tightness cannot be achieved.
An alternative to the known O ring seals can be found in the static sealing elements such as metal C rings which are, however, only suitable with restrictions for a use in lightweight housings, which are produced from aluminum as a rule, and are very sensitive. Furthermore, this seal cannot be manufactured for more complex shapes.
It is already known with respect to the corrosion resistance of the housing to provide it with an anti-corrosion coating. The surface protection of the metal housing, however, has to have good local conductivity to be able to satisfy existing demands such as lightning, bonding as well as electromechanical compatibility (EMC). The previously known conductive surface coatings only provide a moderate corrosion protection. It is, however, not practicable from a technical production aspect to provide the surface up to the round seal with a non-conductive high corrosion protection and to apply a conductive surface protection after the attachment of the seal.
Alternatively to the previously known seals such as metal seals and FVMQ, no sealing technologies are known which satisfy the high demands on such housings, namely gastight with a very low steam permeation, vibration resistance, media resistance and long-term stability. Such housings, which are used in aeronautic technology, have to be very temperature resistant for this reason.
It is therefore the object of the present disclosure to provide a housing structure which can in particular be used in aeronautic technology, which is hermetically sealed, on the one hand, and which significantly reduces the arising of corrosion, on the other hand, which improves leak-tightness and steam permeation and which does not negatively influence EMC behavior and bonding behavior.
This object is achieved in accordance with the present disclosure by a housing arrangement having the features of claim 1 as well as by a sealing structure having the features of claim 10.
The housing arrangement in accordance with the present disclosure which has at least one housing for connecting a plug-in connector is provided with at least one seal which is placed in an opening provided in the housing and/or in a plug flange of the plug-in connector and which comprises a milled portion. In the solution in accordance with the present disclosure, a groove is thus no longer necessary in which the seal is placed, but only a milled portion in the plug flange or in the housing is required in which the seal is precisely attached. With this arrangement, the leak-tightness and the handling (the production costs) are noticeably improved and the corrosion formation is additionally considerably reduced since here a more or less punctiform sealing takes place and not along the whole connection surface between the housing and the plug as in the above-named solutions known from the prior art. The milled portion allows a defined pressing of the seal and a good handling in the installation of the seal.
In accordance with the present disclosure, the seal is a compressible seal which has an elastic portion. The leak-tightness can be substantially improved with this seal in comparison with the previously known seals of fluorosilicone rubber, with the corrosion formation additionally able to be considerably reduced. The compressible seal in accordance with the present disclosure protects the structure from ingressing media and thus makes an additional corrosion protection superfluous.
The housing may have a cover, with the at least one opening, which is formed as a milled portion, is provided at the connection of the cover to the housing. The milled portion can be formed both at the upper region of the housing adjacent to the cover and at the lower region of the cover adjacent to the housing. The housing can thus not only be sealed in the region of the plug-in connection, but also in a gas-tight manner at the cover. The region of the plug connection to the housing and of the connection of the cover to the housing is protected better against corrosion by the structure in accordance with the present disclosure, wherein the electromagnetic compatibility and the bonding can be improved.
The seal can have a geometry of any desired complexity and can be pressed locally more so that a high leak-tightness is ensured.
An embodiment of the present disclosure provides that a surface coating is applied in the form of a non-conductive and resistant corrosion protection before the installation of the seal. The surface coating may be applied to the housing or to the plug at the environmental side up to the regions on which the seal lies.
The bonding connection between the plug connector and the housing may be realized with a conductive surface coating, e.g. a chromatization.
The respective coatings may be applied in the at least one cut-out provided in the housing and/or in the cover of the housing.
The structural principle of a seal at a housing cover is the same as the structure at the plug-in connectors. The seal may be formed as a flat seal and can also be used in complex housing contours. A cut-out in the cover or in the housing serves as an installation aid for the introduction of the seal in accordance with the present disclosure and guarantees a defined pressing of the seal. In the case of high leak-tightness demands, the seal can be pressed locally more in ring shape by a stress point.
The compressible sealing structure in accordance with the present disclosure as claimed in claim 12 protects the whole housing from ingressing media and thus makes an additional corrosion protection superfluous. The surface coating at the surfaces adjacent to the seal can be applied in the form of a non-conductive and resistant corrosion protection, wherein the bonding connection and EMC connection between the plug and the housing can be realized by a conductive surface coating, e.g. a chromatization.
The present disclosure will now be explained in more detail with reference to an embodiment and to the drawing.